The present invention relates to electrically shielding enclosures, commonly referred to as screen rooms, for protection from electrical, electrostatic and magnetic fields, and in particular to an improved construction of such a screen room which requires minimum numbers of elements and enables the room to be readily assembled and disassembled without loss of shielding effectiveness.
Shielding efficiency is related to conductivity and nonpermeability, and it is well known that continuous electrical conductivity between contiguous points in a shielding element affords a pronounced efficiency as a radial wave shield in the intermediate and lower wave bands. However, by utilizing multiple mutually spaced shielding enclosures, the extent of shielding may be further enhanced and extended over a wider range of frequencies.
Various materials are known to possess shielding characteristics which, to some degree, serve the purpose of isolating a space between or against electrical, magnetic and electrostatic wave penetrations. In prior shielded enclosures of this type, a copper mesh screen has conventionally been used and considered an effective shielding material. In construction of a double shielded isolation room, each individual shield must completely encompass the space to be shielded, one within the other, yet maintain continuity of conduction between consecutive sections of the same shield and at the same time maintain electric isolation of the spaced apart shields.
In joining adjacent panels to form a double isolated screen room, it is necessary not only to maintain continuity of conduction between sections of the shields on inner and outer walls of the room as well as electrical isolation between the shields, but also to provide a means for positively securing the panels in tight and rigid relationship. It is also desirable to permit the connection of adjacent panels with a minimum amount of hardware and shielding joining members while at the same time enhancing the effectiveness of the shielded enclosure, and to provide a solid, rigid structure to eliminate the possibility of separation of the panels.
Prior electrically isolating screen rooms have usually been set up with a space around them which was at least temporarily required by workmen at the time of assembling and securing the screen room panels in place from outside the rooms. External assembly on some screen rooms sometimes resulted in an overall shifting of clamped elements in several directions, which inherently tended to loosen pressure contacts desired between shielding screen edges. Leakage spaces that might be undetectable mechanically could occur and variably lower the decibel test rating of some of the rooms that were otherwise identical. Also difficulty could be experienced with externally installing one or more of the ceiling panels to the tops of the side walls. Moreover, for on-site assembly, time and labor for setting up screen rooms has heretofore been quite expensive, particularly when engineering supervision or sorting of many complicated parts, like a puzzle, is required, or complicated joints and fixed assembly sequences are involved.
U.S. Pat. Nos. 3, 783,174 and 3,790,696 to the present inventor, the teachings of which are specifically incorporated herein by reference, solved many of the foregoing problems. However, the screen rooms of those patents require a considerable number of members, separate from the side, ceiling and floor panels, which along with fasteners are required to connect the various panels, which adds complexity and expense to the screen room, its assembly and disassembly.